Radio communication systems, such as trunked radio systems or cellular systems, are known to include a system controller, a plurality of base sites, and a plurality of communication units, such as mobile radios, portable radios, or radiotelephones. Each base site serves a corresponding service coverage area and typically provides at least one traffic channel and a control channel to the communication units that are located within the base site's service coverage area. The traffic channels are utilized to convey information between communication units or between communication units and public switched telephone network (PSTN) subscribers. The control channel is used to convey system information between the communication units and a particular base site.
During a typical communication, a communication unit moves throughout service coverage areas of the system. The movement of the communication unit requires the system controller to track the location of the communication unit within the system to enable the system controller to alert the communication unit when a call involving the communication unit is received at the system controller. That is, the system controller must know approximately where the communication unit is located in order to assign an appropriate base site to support a communication for the communication unit.
One known approach to tracking communication unit movement is known as the coverage area update approach. The coverage area update approach requires a communication unit to report, or register, each time the communication unit enters a different service coverage area. The communication unit monitors the system control channel to obtain the identification of the base site serving the coverage area containing the communication unit. Upon observing a change in the base site identification on the control channel, the communication unit transmits an inbound message on the control channel to register with the system controller in the new service coverage area. Therefore, when a communication arrives at the system controller for a particular communication unit, the system controller simply transmits the communication to the communication unit via the base site serving the service coverage area containing the communication unit. Although this approach facilitates expedient call set-up because the system controller always knows the service coverage area within which a particular communication unit is located, the approach requires substantial inbound signaling on the control channel to maintain location reporting accuracy to within a base site's service coverage area. Excessive inbound control channel activity results in inefficient use of both the control channel and system controller resources that are necessary to process the abundance of registration messages. Due to its excessive inbound control channel activity, coverage area tracking is generally used only when tracking a communication unit that is actively participating in a communication.
Another known approach to tracking communication unit movement is known as the location area update approach. The location area update approach requires a communication unit to report, or register, each time the communication unit enters a different so-called location area. A location area typically comprises multiple base site service coverage areas and, accordingly, is serviced by multiple base sites. With this approach, the communication unit monitors the system control channel to obtain the identification of the location area containing the communication unit. Upon observing a change in the location area identification on the control channel, the communication unit transmits an inbound message on the control channel to register with the system controller in the new location area. Since the number of location areas is generally less than the number of service coverage areas, the communication unit registers proportionately less with the location area update approach than with the coverage area update approach. Thus, the location area update approach involves substantially less inbound control channel activity than does the coverage area update approach.
With location area tracking, when a communication arrives at the system controller for a particular communication unit, the system controller pages the communication unit from all the base sites serving the location area containing the communication unit. Upon receiving an acknowledgment of the page from the communication unit, the system controller transmits the communication to the communication unit via the base site that received the page acknowledgment. Thus, although the location area update approach reduces the amount of inbound control channel activity as compared with the coverage area update approach, the location area update approach increases the amount of outbound control channel activity (i.e., pages). Due to its excessive amount of outbound control channel activity, location area tracking is generally used only when tracking a communication unit that is not actively participating in a communication.
Packet data communications are becoming more popular in trunked radio communication systems. The nature of packet data communications is such that a single communication is comprised of multiple data packets. In such systems, the system controller is divided into two entities, the controller and a packet data router. The controller performs registration, paging, and other system control functions. The packet data router extracts a destination address (e.g., Internet protocol (IP) address) for each received data packet from a network layer (layer 3) of the packet and, in response to signaling from the controller, directs the received data packets to the appropriate base sites for subsequent transmission to the appropriate target communication units. In addition, the various data protocols utilized in the wireline packet routing network (e.g., the Internet) to convey the data packets often causes groups of packets of the communication to arrive at the packet data router/controller at different times. Thus, in many circumstances, the router/controller must contact the communication unit more than one time to provide the complete packet data communication to the communication unit.
In a packet data communication, a communication unit is considered to be actively participating in a communication only during the time when either the data packets are being delivered to the communication unit or the communication unit is transmitting its data packets. When the communication unit is awaiting additional packets to complete the communication, the communication unit is not considered to be actively participating in the communication. Therefore, when the system controller or packet data router is transmitting data packets to the communication unit, the communication unit utilizes coverage area tracking; whereas, when the system controller or packet data router is awaiting more data packets to the complete the communication, the communication unit utilizes location area tracking. Consequently, the system controller must page the communication unit on more than one occasion to deliver a single packet data communication. The subsequent number of pages undesirably increases the amount of outbound control channel activity per communication.
Therefore, a need exists for a method and apparatus of providing packet data communications to a communication unit in a radio communication system that efficiently utilizes inbound and outbound control channel resources.